Apparatus for the hydraulic classification of solids

ABSTRACT

Hydraulic classifying apparatus for liquid slurries of mixed coarse and fine particles includes first and second syphon connected containers and means for maintaining syphon flow between the containers while continuously feeding slurries to be separated to the first container. An enlarged inlet portion of the syphon is positioned within the first container and together with an upstanding central outlet defines a separating zone so that coarse particles settle through the central outlet and fines continue through the syphon to the second container.

United States Patent Dorph May 16, 1972 54] APPARATUS FOR THE HYDRAULIC 3,452,862 7/1969 Amadon et a1. ..209/2 CLASSIFICATION OF SOLIDS FOREIGN PATENTS OR APPLICATIONS [72] inventor: Thor Dorph, 5 West 63rd Street, New

Y0rk,l l.Y. 10023 [22] Filed: Dec. 31, I969 [21] Appl. No.: 889,608

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 853,324, Aug. 27,

1969, abandoned.

[52] U.S. Cl ..209/l6l, 209/210 [51] Int. CL... ..B03b3/34 [58] Field ofSearch ..209/l58l61,2l0, 209/12 [56] References Cited UNITED STATES PATENTS 1,537,424 5/1925 Elms ..209/2l0 SOURCE OF (DARSE DISCHARGE 117,250 6/1958 U.S.S.R. ..209/l58 Primary Examiner-Frank W. Lutter Assistant Examiner-Ralph J. Hill Attorney-Kemon, Palmer & Estabrook ABSTRACT Hydraulic classifying apparatus for liquid slurries of mixed coarse and fine particles includes first and second syphon connected containers and means for maintaining syphon flow between the containers while continuously feeding slurries to be separated to the first container. An enlarged inlet portion of the syphon is positioned within the first container and together with an upstanding central outlet defines a separating zone so that coaIse particles settle through the central outlet and fines continue through the syphon to the second contamer.

12 Claims, 4 Drawing Figures 1 Q FINES DISCHARGE PATENTEDMAY 1 6 I972 SHEET 1 [IF 3 SOURCE OF FINES DISCHARGE FIG] COARSE DISCHARGE INVENTOR THOR DORPH BY 14% flaa hw ATTORNEYS PATENTEDHAY 16 m2 3. 662.885

sum 2 BF 3 FL'VE55XPE9HSCHARGE 22 ZONE /30 40\ PRIMARY 0 V; SEPARATING 0 BY pw 7* 5 ATTORNEYS PATENTEUMAY 16 I972 SHEET 3 UF 3 TO AIR VACUUM SOURCE AIR fi --nNEs SYPHON DISCHARGE QQEQQbkE AIR SUPPLY ENVENTOR THOR UORPH ATTORNEYS APPARATUS FOR THE HYDRAULIC CLASSIFICATION OF SOLIDS Cross Reference to Related Application This application is a continuation-in-part of my prior copending application, Ser. No. 853,324 filed Aug. 27, 1969 and now abandoned.

BACKGROUND OF THE INVENTION While the apparatus of this invention is thought to have wide utility wherever hydraulic classification of mixed size particles is desired, it is thought to have primary utility-in the separation and classification of stone, mineral ore or other like actual materials, the density of which is greater than that of the fluid in which they are suspended mixed with water and known as slurry or pulp. A common example is the pulp in the closed circuit of a ballmill grinding process for ore treatment. The usual particle sizes encountered in these processes range from approximately three-eighths inch to very fine dust-like particles which are known as slimes or fumes. In certain industries the slimes and fumes are undesirable product sizes. The present apparatus therefore is particularly adapted for the removal of such small particles as well as to remove usable particles as efficiently as possible. By separating and removing the desirable particle sizes from the grinding recycle flow, the amount of overgrinding may be reduced. The primary object of the present invention is to provide an efficient ore classifying apparatus and method which has a minimum of moving parts, which utilizes a condition of directly sustaining maximum exposure of suspended solids contents to separating flow of water and particle interaction with or because of suspension of solids in a vertically upwardly directed fluid flow and which operates with a minimum of external power consumption.

BRIEF SUMMARY OF THE INVENTION In accordance with the present invention, the slurry or pulp containing the mixed particle sizes is fed into the upper portion of a first stationary container having a centrally disposed outlet in the bottom thereof. This container is connected by a syphon to a second container and the primary separating zone is set up between the inlet to the syphon and the outlet in the first container. By controlling the flow rate through the syphon, a continuous separation is effected with the coarse particles exiting from the first container through the centrally disposed bottom thereof and the desirable fines along with slimes and fumes pass on through the syphon to the second container.

BRIEF DESCRIPTION OF THE DRAVINGS FIG. 1 is a schematic diagram of a preferred embodiment of the present invention;

FIG. 2 is an enlarged view of a portion of FIG. 1;

FIG. 3 is a view similar to FIG. 1 showing an alternative embodiment; and

FIG. 4 is a view similar to FIG. 3 showing a further altemative embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to FIG. 1, it will be seen that the apparatus comprises basically a pair of containers and 12, the interiors of which are interconnected by means of a syphon 14. In order to maintain syphon flow, the syphon 14 preferably includes a dome 16 which is connectable to a source of vacuum as indicated. The rate of syphon flow between the two containers could be controlled in any one of a number of known ways but as indicated in FIG. 1, one possibility is a discharge nozzle 18, the level of which is adjustable. An input feed conduit is shown at 20 which leads to an annular feed trough 22 having an emergency overflow at 24. The inner wall of the trough 22 is conveniently the outer wall of the container 10 so that the slurry fed to the trough 22 overflows the outer wall of the container 10 to enter the upper portion thereof.

Preferably the container 10 includes a reentrant bottom portion 26 which surrounds an outlet conduit 28. The inlet end of the syphon 14 is enlarged as shown at 30. Together with the reentrant portion 26 of the container 10, the enlarged inlet of the syphon 14 defines an annular feed nozzle 32 which enlarges in the direction of upward fluid flow.

FIG. 2 is an enlarged view of the separating zone and the following description of the operation of this apparatus represents the inventors opinion as to the mechanics of the operation.

Under conditions of through flow, that is assuming a constant input of slurry or pulp to the conduit 20 and a constant outflow through the syphon 14 and the discharge nozzle 18 of the container 12, the separating process is believed to operate in the following manner. The flow as it proceeds from the bottom of the container 10 upwardly through the annular feed nozzle undergoes a drop in velocity due to the cross sectional enlargement of the feed nozzle in the direction of flow. With a proper correlation between flow velocity and desired particle separation, it is believed that a substantially conical stagnant zone is created immediately above the discharge conduit 28 as indicated in FIG. 2. In the annular area surrounding the stagnant zone there is in effect a zone in which the heavier coarse particles drop out in diminishingly smaller sizes as the flow progresses upwardly. These coarse particles are displaced laterally by subsequent flow into the stagnant zone where they settle downwards to the coarse discharge outlet. At some level in the upward flow in the separating zone only desired fine particles and smaller remain in the flow to proceed through the syphon 14 to the second container 12 and eventually out the discharge noule 18. It is believed that due to the change in direction of flow at entry into the feed nozzle that there is likely an initial segregation by centrifugal force of the heavier particles and that they tend to congregate adjacent to the inner wall of the reentrant section. This, of course, places them more nearly adjacent the discharge conduit 28 when they reach a point in the separating zone of sufficient altitude to overlie the discharge conduit 28 and therefore settle out at that point.

By way of further analysis, it is also believed that particles which are left teetering in the primary separating zone are acted on by the continuing flow and other particles which tends to create a steady movement of the heavier particles into the stagnant zone and into the discharge conduit. The actual discharge of the coarse particles settling in the coarse discharge conduit is unhindered gravity settling.

Turning now to FIG. 3 of the drawings, a slightly modified form of the apparatus described hereinbefore is shown. Since some of the parts are duplicates to those shown in FIGS. 1 and 2, identical reference numerals are used for those parts. The basic difference between the apparatus in this figure and that in the preceding figures in that an annular nozzle is arranged around the coarse discharge conduit 28. This nozzle identified by the reference numeral 36 is fed from an annular header of distribution pipe 38 from a source 40 of either water or air, or perhaps both, under pressure. The output of the nozzle 36 is, of course, vertically upward in the same direction as the general path of flow through the separating chamber. In addition, there is also a baffle member 42 positioned at the upper side of the separating chamber.

The operation of the separator shown in this figure is substantially the same as the one shown in FIGS. 1 and 2. The purpose of injecting air or additional water or a combination of both through the nozzle 36 is simply to provide an additional upward flow of fluid at a velocity which is sufficient to move fines away from the coarse discharge outlet. Such additional flow may be controlled so as not to impede the movement of coarse particles into the coarse discharge outlet. It is contemplated that in cases where the input to the separator contains a high proportion of coarse particles, that use of additional fluid flow through the nozzle 36 may be beneficial to insure that the fines are not entrapped with the coarse particles and discharged along therewith. The location of the nozzle 36 adjacent the innermost wall of the feed throat is important because the flow of the slurry to be separated will be slower adjacent to the nozzle wall because of skin or surface friction and it is therefore at this point that perhaps some flow assistance is needed in order to insure that all particles are carried upwardly into the separating zone.

In order to provide for control regulation of the coarse particles under varying flow rates, a conventional rotary discharge valve indicated at 44 may be employed. This valve may be driven by a variable speed motor 46, the speed of which is controlled by the height of the accumulated coarse particles in the coarse discharge conduit 28. A plurality of sensing means indicated at 48, 50 and 52 will sense the level of the accumulated separated coarse particles and govern the speed of rotation of the discharge valve accordingly. Obviously other discharge mechanisms may be utilized.

While the apparatus shown in FIG. 4 is in many ways similar to that shown in FIG. 3, there are some structural differences which are thought to yield a more efficient separation. The annular chamber 60 which surrounds the lowermost end of the enlarged syphon inlet 30 is supplied with air under controlled pressure. A, circumferentially arranged series of nozzles 62 communicate the annular chamber 60 with the interior of the syphon inlet at points which lie below the primary separating zone. The wall of the syphon inlet 30 is tapered upwardly as shown so that the air bubbles which tend to rise through the liquid will form an upwardly moving air curtain along the inner side wall of the separating chamber.

As is well known, for non-turbulent fluid flow through a conduit, there is a velocity distribution which reaches a maximum at the center of the flow and approaches zero at the walls of the vessel in which the flow is taking place. With the addition of air to create the air bubble curtain as described above, the zone of zero flow velocity adjoining the wall of the separating chamber is destroyed and the fluid flow at that point approaches a higher value so that the velocity distribution across the fluid flow section then approaches a more uniform figure. An ideal condition, of course, would be a uniform velocity figure throughout the section of fluid flow but, as a practical matter, this is not obtainable. With the air bubble curtain, however, the desired condition is nevertheless approached and there should be fewer coarse particles carried by the center of the section of flow through to the fines discharge.

The additional air in the fluid stream could be withdrawn at the dome 16 of FIG. 1. It might, however, be desirable to withdraw the additional air at a point ahead of the dome 16 and one possible arrangement for doing this is shown in FIG. 4. This construction includes an annular air trap chamber 64 together with a means for controlling the withdrawal of air therefrom in the event that the exhaust discharge opening is at negative gauge pressure. In that event, it may be necessary to utilize an automatic control means, for example, a closed chamber 66 connected at one end to the trap chamber 64 and at its upper end to perhaps the same source of vacuum which is connected to the bell 16 of FIG. 1. An automatic control valve 68 would be controlled by the water level within the chamber 66.

To take further advantage of the increased efficiency brought about by the modification of the flow pattern due to the presence of the rising curtain of air bubbles along the interior of the separating chamber, FIG. 4 also shows a modification of the inlet feed nozzles which is specifically different from the form shown in either of FIGS. 1 or 2. In this instance, a kind of gooseneck pattern is achieved by an inward bulge in the lower portion of the chamber 60 as shown at 70 and a corresponding inwardly curved portion 72 of the reentrant portion of the first vessel. The result is that the inlet feed is directed more nearly along the inner walls of the separating chamber and away from the coarse discharge chamber so that the solids will be thrown outwards and travel upwardly through the feed nozzle along the outer boundary of the separating chamber. They will therefore enter the separating zone as far as possible from the coarse discharge chamber entry. Due to the drop in the midstream velocity, this will maintain the particles in fluid flow for a longer period of time and therefore further increase the desired degree of separation between coarse and fine particles.

While preferred embodiments of the present invention have been herein shown and described, applicant claims the benefit of a full range of equivalents within the scope of the appended claims.

I claim:

1. Hydraulic classifying apparatus comprising in combination:

a. an open top annular first container having an annular reentrant bottom concentrically surrounding a central vertical outlet conduit, said conduit extending through said re-entrant bottom and opening into said container;

b. a second open top container at least the bottom of which is positioned below the level of the bottom of said first container;

c. a syphon interconnecting said containers, said syphon having at one end an enlarged annular inlet portion positioned within said first container and defining with the inner surface of the outer wall of .said container a confined feed area and the inner surface of said syphon inlet surrounding and defining with said re-entrant portion of said container an annular feed nozzle area enlarging progressively upwards;

d. means for continuously feeding to the upper portion of said first container a liquid slurry having coarse and fine particles to be separated;

e. means for maintaining a syphon flow from said first to said second container; and

f. means for controlling the rate of syphon flow; whereby a separating zone is established within said enlarged inlet portion of said syphon above the innermost terminus of said re-entrant portion of said first container so that coarse particles settle through said central outlet conduit and fine particles pass on through said syphon to said second container.

2. The combination defined by claim 1 in which said means for maintaining syphon flow comprises means for connecting a source of vacuum to said syphon at a point between said first and second containers. I

3. The combination defined by claim 1 in which said means for controlling the rate of syphon flow comprises a vertically adjustable outlet connected to said second container.

4. Apparatus as defined by claim 1 including means communicating with the interior of said first container for injecting an additional fluid under pressure, the points of injection being such that flow due to said additional fluid is upward along the side wall of said reentrant portion.

5. Apparatus as defined by claim 4 in which said additional fluid is water.

6. Apparatus as defined by claim 4 in which said additional fluid is air.

7. Apparatus as defined by claim 4 in which said additional fluid is a mixture of air and water.

8. Apparatus as defined by claim 1 including means for varying the rate of discharge of coarse particles from said outlet conduit in accordance with the accumulation of particles therein.

9. Hydraulic classifying apparatus comprising in combination:

a. an open top annular first container having an annular reentrant bottom concentrically surrounding a central outlet conduct, said conduit extending through said re-entrant bottom and opening into said container;

b. a second open top container at least the bottom of which is positioned below the level of the bottom of said first container;

c. a syphon interconnecting said containers, said syphon having at one end an enlarged upwardly tapered annular inlet portion positioned within said first container and defining with the inner surface of the outer wall of said container a confined feed area and the inner surface of said syphon inlet surrounding and defining with said reentrant portion of said container an annular feed nozzle area enlarging progressively upwards;

d. means for continuously feeding to the upper portion of said first container a liquid slurry having coarse and fine particles to be separated;

e. means for maintaining a syphon flow from said first to said second containers;

f. means for injecting air through the lower wall of said typhon inlet portion to form an air bubble curtain along the entire inner surface of said typhon inlet; and

g. means for controlling the rate of syphon flow, whereby a separating zone is established within said enlarged inlet portion of said typhon above the innermost terminus of said re-entrant portion of said first container so that coarse particles settle through said central outlet conduit and fine particles pass on through said syphon to said second container.

10. Apparatus as defined by claim 9 in which said means for injecting air comprises an annular manifold surrounding the exterior surface of the lower end of said syphon inlet portion and a plurality of nozzle openings through the wall of said inlet portion communicating said manifold with the interior of said syphon inlet at apoint below said separating zone.

11. Apparatus as defined by claim 9 and including an annular air trap chamber surrounding the upper end of said syphon inlet and means for withdrawing air from said chamber.

12. Apparatus as defined by claim 9 and including means communicating with the interior of said first container for injecting an additional fluid under pressure, the point of injection being such that flow due to said additional fluid is upward along the side wall of said reentrant portion. 

1. Hydraulic classifying apparatus comprising in combination: a. an open top annular first container having an annular reentrant bottom concentrically surrounding a central vertical outlet conduit, said conduit extending through said re-entrant bottom and opening into said container; b. a second open top container at least the bottom of which is positioned below the level of the bottom of said first container; c. a syphon interconnecting said containers, said syphon having at one end an enlarged annular inlet portion positioned within said first container and defining with the inner surface of the outer wall of said container a confined feed area and the inner surface of said syphon inlet surrounding and defining with said re-entrant portion of said container an annular feed nozzle area enlarging progressively upwards; d. means for continuously feeding to the upper portion of said first container a liquid slurry having coarse and fine particles to be separated; e. means for maintaining a syphon flow from said first to said second container; and f. means for controlling the rate of syphon flow; whereby a separating zone is established within said enlarged inlet portion of said syphon above the innermost terminus of said reentrant portion of said first container so that coarse particles settle through said central outlet conduit and fine particles pass on through said syphon to said second container.
 2. The combination defined by claim 1 in which said means for maintaining syphon flow comprises means for connecting a source of vacuum to said syphon at a point between said first and second containers.
 3. The combination defined by claim 1 in which said means for controlling the rate of syphon flow comprises a vertically adjustable outlet connected to said second container.
 4. Apparatus as defined by claim 1 including means communicating with the interior of said first container for injecting an additional fluid under pressure, the points of injection being such that flow due to said additional fluid is upward along the side wall of said reentrant portion.
 5. Apparatus as defined by claim 4 in which saId additional fluid is water.
 6. Apparatus as defined by claim 4 in which said additional fluid is air.
 7. Apparatus as defined by claim 4 in which said additional fluid is a mixture of air and water.
 8. Apparatus as defined by claim 1 including means for varying the rate of discharge of coarse particles from said outlet conduit in accordance with the accumulation of particles therein.
 9. Hydraulic classifying apparatus comprising in combination: a. an open top annular first container having an annular re-entrant bottom concentrically surrounding a central outlet conduct, said conduit extending through said re-entrant bottom and opening into said container; b. a second open top container at least the bottom of which is positioned below the level of the bottom of said first container; c. a syphon interconnecting said containers, said syphon having at one end an enlarged upwardly tapered annular inlet portion positioned within said first container and defining with the inner surface of the outer wall of said container a confined feed area and the inner surface of said syphon inlet surrounding and defining with said re-entrant portion of said container an annular feed nozzle area enlarging progressively upwards; d. means for continuously feeding to the upper portion of said first container a liquid slurry having coarse and fine particles to be separated; e. means for maintaining a syphon flow from said first to said second containers; f. means for injecting air through the lower wall of said typhon inlet portion to form an air bubble curtain along the entire inner surface of said typhon inlet; and g. means for controlling the rate of syphon flow, whereby a separating zone is established within said enlarged inlet portion of said typhon above the innermost terminus of said re-entrant portion of said first container so that coarse particles settle through said central outlet conduit and fine particles pass on through said syphon to said second container.
 10. Apparatus as defined by claim 9 in which said means for injecting air comprises an annular manifold surrounding the exterior surface of the lower end of said syphon inlet portion and a plurality of nozzle openings through the wall of said inlet portion communicating said manifold with the interior of said syphon inlet at a point below said separating zone.
 11. Apparatus as defined by claim 9 and including an annular air trap chamber surrounding the upper end of said syphon inlet and means for withdrawing air from said chamber.
 12. Apparatus as defined by claim 9 and including means communicating with the interior of said first container for injecting an additional fluid under pressure, the point of injection being such that flow due to said additional fluid is upward along the side wall of said reentrant portion. 